1. Field of the Invention
The present invention generally relates to methods and apparatuses for testing or aligning the various parts of a processing system. Specifically, the present invention relates to methods and apparatuses for leveling and aligning the processing system and the various structures within the processing system that support and/or transfer processing objects, such as substrates, through the processing system so that the processing system and each structure is substantially level and so that each structure receives, supports and/or transfers the substrates in substantially the same inclination and without slippage of or damage to the substrates.
2. Background of the Related Art
Processing systems for processing 100 mm, 200 mm, 300 mm or other diameter substrates are generally known. Typically, such processing systems have a centralized transfer chamber mounted on a monolith platform. The transfer chamber is the center of activity for the movement of substrates being processed in the system. One or more process chambers mount on the transfer chamber at slit valves through which substrates are passed by a substrate handler, or robot. Access to the transfer chamber from the clean ambient environment is typically through one or more load lock chambers attached at other slit valves. The load lock chambers may open to a very clean room, referred to as the white area, or to an optional substrate handling chamber, typically referred to as a mini-environment.
In addition to the substrate handler disposed within the transfer chamber, a processing system may have several other structures, including, but not limited to, indexers in the load lock chambers, lift pins in the process chambers, and substrate chucks in the process chambers, which will support or handle the substrates in one manner or another. The lift and support structures within the processing system may exchange substrates more rapidly, without slippage or backside contamination of the substrates, if the lift and support structures are level. Additionally, the extremely fine and delicate nature of the circuits and other structures being constructed on the substrates may require that the processing system as a whole, and particularly each substrate support structure, be set as near to level as possible. Typically, assemblers or operators of the processing systems may try to ensure that, at a minimum, the various substrate support structures are in alignment relative to each other, so that even if each support structure is not perfectly level, at least they are all at the same inclination. Additionally, the assemblers or operators will attempt to ensure that the substrate support structures, which move the substrates laterally, accelerate and decelerate at suitable rates and without discontinuous, or jerking, motion, so that the substrates do not slip on the support structure. Failure to ensure that the processing system and/or each of the substrate support structures is properly level and/or aligned and is operating smoothly may cause damage to or improper processing of the substrates and can reduce the throughput of the processing system since substrate exchanges may not be performed at maximum speed.
Relative alignment of the substrate support structures is typically more important than absolute leveling of the entire processing system since substrate exchange handling can result in significant slippage due to improper alignment. When the substrate support structures, within a processing system, are improperly aligned, however, the support structures do not hold the substrates at about the same inclination, or tilt. Thus, when one support structure transfers a substrate to another support structure, such as when the lift pins remove a substrate from a blade of the transfer chamber substrate handler or place a substrate onto the substrate chuck in a process chamber, one point of the substrate will always touch the receiving support structure before other points do. If substantial motion occurs prior to the remaining points making contact, then the substrate can slip. In this manner, potentially contaminating particles may be scraped from the contacting points of the substrate causing backside contamination of the substrate. These particles may eventually work their way around to the top of the substrate and be deposited on the processed surface of the substrate, thereby contaminating the micro circuits or other structures constructed thereon. Additionally, when the substrate does not touch a receiving support structure with all points in very close alignment, then the substrate may be shifted from its proper, or expected, position, so that the substrate is off-center. An off-center substrate may undergo uneven or otherwise improper processing or may come in contact with surfaces or objects within the processing system that will contaminate the substrate, create potentially contaminating airborne particles or even break the substrate. Thus, exchanges of the substrate between lifting or supporting structures within the processing system require a coplanar interface. If the exchange is not coplanar, then the substrate will have the propensity to slip, resulting in misalignment and backside contamination of the substrate.
When a processing system as a whole is improperly leveled, the system chambers, such as the transfer chamber, are inclined at an angle and can cause problems with the handling and processing of substrates and can exacerbate the problems with substrate support structures that are further inclined relative to the processing system. Since the substrate support structures are mounted to the processing system, if the processing system is inclined and the support structures are level relative to the processing system, then the support structures will also be inclined, though the support structures may, nevertheless, be aligned with each other. When the processing system is inclined, but the support structures are aligned, then the processing system may still operate properly, but possibly at a lower than optimum speed. Additionally, performance of certain functions that are sensitive to gravity may be affected by the inclination of the system. When a transfer chamber substrate handler, for example, accelerates a substrate in a manner that may be appropriate for a level system, the substrate may, nevertheless, slide off-center due to the inclination, thereby exposing the substrate to potential damage from particles that may be generated by the slide or to potential collision with a surface or object in the processing system that requires a relatively close centering tolerance of the substrate for clearance.
The substrate support structures typically may be leveled independently within the processing system. Thus, after the transfer chamber and the processing chambers are leveled as a whole, the transfer chamber substrate handler or the process chamber lift pins or chuck may be additionally leveled independently. It is even possible for a substrate handler to be fairly level while the transfer chamber is significantly inclined, or vice versa. In such manner, the substrate handler may be aligned with an opening through which it passes substrates to and from a process chamber on one side of the transfer chamber, yet be out of alignment with an opening for a process chamber on the opposite side of the transfer chamber. Therefore, the transfer chamber substrate handler must be fairly closely aligned with the inclination of the transfer chamber to permit proper functioning of the entire system.
FIG. 1a shows a prior art method of determining the inclination of a transfer chamber substrate handler 10. The transfer chamber 12 is shown with a lid 14 partially lifted to expose the interior of the chamber body 16. The substrate handler 10 is mounted in about the center of the transfer chamber 12 and rotates about a center point. The substrate handler 10 extends a blade 18 to insert a substrate 20 through a slit valve opening 22 to access a process chamber (not shown) or a load lock chamber (not shown) mounted to the facets 24. To determine the inclination of the blade 18, an operator places a level, such as a bubble level, 26 onto the blade 18 and reads the inclination through a window in the level 26. The level 26 may be placed directly onto the blade 18, or the level 26 may be placed onto a substrate 20 sitting on the blade 18. The inclination of the blade 18 must be measured in each relevant direction with the blade 18 retracted as shown and with the blade 18 extended through the slit valve 22, so the substrate handler 10 can function properly throughout all of its movements. The actual leveling of the substrate handler 10 may involve adjusting the transfer chamber 12 relative to a support platform (not shown), adjusting the base 28 relative to the transfer chamber 12 and adjusting the arms 30, linkages 32 and blade wrist 34.
There are several problems with the measurement method depicted in FIG. 1a. The substrate handler 10 must be still, for example, so the operator can read the level 26, since the acceleration of the blade 18 would affect the level 26. Therefore, the inclination of the blade 18 while the blade is in motion is unknown. Additionally, the lid 14 must be removed, so the operator can access the substrate handler 10. Therefore, the processing system must be shut down, so the lid 14 can be removed, intruding into the clean environment; and the ambient air must be more highly filtered of particles than usual, so the interior of the transfer chamber 12 is not contaminated. Also, the level 26 does not fit through the slit valve openings 22, so the operator must remove the level 26 from the blade 18 to extend the blade 18 into a process chamber and then place the level 26 back onto the blade 18. Therefore, the process chamber must also be opened, exposing the process chamber to possible contamination and further increasing the down-time of the system. Furthermore, the levels used to measure the inclination typically can resolve the inclination to within only two or three degrees accuracy, are highly dependent on the skill of the operator who is reading the level, and can affect the blade deflection due to the weight of the level, itself. Therefore, process systems or processes that are particularly sensitive to misalignment may be adversely affected. Because of the problems and difficulties with performing this measurement method, some operators may elect not to make these measurements very thoroughly or even not to make them at all.
FIG. 1b shows another prior art method for determining the inclination of a substrate 20 seated on a substrate handler blade 18 within a processing system. A stationary laser 36 mounts to a surface 38 in the processing system, typically the floor of the transfer chamber, and directs a laser beam 40 into the path of the substrate 20 as the substrate moves through the system in the direction of arrow A. This method may be performed during normal processing of substrates in the processing system or just whenever needed. When the leading edge 42 of the substrate 20 intersects the laser beam 40, the laser 36 detects the distance to the substrate 20. Then just before the trailing edge 44 moves out of the laser beam 40, the laser 36 detects the distance to the substrate 20, again. If the two distances are about the same, then the substrate 20 is aligned with the surface 38 of the processing system in the particular axis measured. However, this method does not determine if the substrate 20 is level. Rather, this method determines the alignment of the substrate 20 relative to the chamber through which it is being transferred, so the problems with an inclined substrate 20 or blade 18, as described above, may still occur. Additionally, this method can determine the inclination of the substrate 20 in only one axis, the direction of movement. Since the laser 36 does not move, if the operator wants to determine the inclination of the substrate 20 in a different axis, then one or more other lasers will have to be mounted in the processing system to determine the distance to other points on the substrate 20. Furthermore, since the laser 36 is not moveable, this method determines the inclination of the substrate 20 at only one location, so if the operator wants to determine the inclination of the substrate 20 at a different location, such as at the opposite side of the transfer chamber, then additional lasers will have to be mounted at that location. Moreover, since the laser 36 is mounted into the processing system, removal of the laser 36 is either impossible or very difficult. Additionally, contaminants may prevent the proper functioning of the optics. Furthermore, a warped substrate may lead the laser sensors to incorrectly determine that the blade or substrate is inclined. Therefore, although this method can be performed without opening the processing system, this method is very inflexible.
During processing, the blade 18 in many processing systems is constantly moving between areas of high and low temperatures, such as hot process chambers and cool load lock chambers. The frequent temperature variations may cause the blade 18 to suffer “blade wilt,” wherein the blade 18 becomes warped due to expansion and shrinkage resulting from the temperature changes. Thus, over time, the blade 18 may be warped out of alignment, so the blade 18 may degrade and hold the substrates at an unacceptable inclination. Other shifting of alignments between the various substrate support structures, due to the wear or slippage from constant movement during processing, may also occur. To reestablish confidence in the alignment of the substrate support structures, the processing system must have built-in inclination detection systems, such as the one shown in FIG. 1b, or the operator must stop the processing system and open it up to diagnose the condition of the support structures with a method such as the one shown in FIG. 1a. Because of the down-time associated with the method shown in FIG. 1a, many operators elect not to perform the method or to wait until the substrate support structures are severely out of alignment and potentially damaging the substrates.
Therefore, a need exists for an apparatus and method for determining the inclination and alignment of various substrate handling mechanisms of a processing system, but that is very flexible, does not intrude into the clean environment of the processing system, is fast, and provides a very thorough diagnosis of the system alignments.